Force gauge



Aug. 14, R C. BUR-|- FORCE GAUGE Filed Dec. L'1, 1942' INVENTOR ROBERT c. BURT I vlfffRsobertC.asadenaaCalifass p fheed AircraftCorporatiqn, k Cali n l pplication December 7, 194.2,SerialNoAGOO I claims. (llj's This invention relates to force gauges and particularly `to a force gauge `adaptedto f measure pressure between the electrode tips yof a spot.

Welding machine. p 1 I f Various'typesof force gauges'have heretofore been `constructeduand used for measuring the pressure `or `force Aexerted between' the "tips of spot welding electrodes, lsuch devices usually being of bulky construction and requiring "wide` separation 'of the welding tips in order to accommodatevthe pressure measuring` device. Under such conditions where the electrodes were separated7 fromthe lnormal Welding position thel pres-4 sures' measuredv were vnot representative `of true 15 operating conditions. v

Tneobject of the present invention is to supply a force gauge which is relatively thinbetween the' points 'of application of the"force to be measured whereby it maybe readily inserted between the welding tips of spot Welding machines and welding electrode pressuresmeasured under conditions in which the electrodes are in the approximate position normallyf occupied 'during Welding operations. I 4 The object is accomplished in general by means of a' device in which the invention is embodied,` comprising anelongated beam "supported near: one end at two relatively closelygspaced points to form ashort, end supported or simple `span por-v tion,` and `a relatively long overhanging cantilever aken f 1Figure 3 is ,5a lfragmentary cross-section -t onlline 3$3of-'Figurefill)1utA f: n n Figure @is a i fragmentary cross-section` of -i an optional rconstriiction of: the portiontof ,theY i appa, ratus=shownin-1gure 3.@1 i '3 f i1 The apparatus isas AfollowsriAv f The base member.'` I'Ilwhich maybe` constructed in the form of arelativcly` long; thin bar, @Orrin any other convenient' shapetserves as awcommon supporti Afor ztheA assemblyzfof: apparatus elements hereinafter enumeratedn` A beam II is supported adjacentzone. endV yof'l therbase member I0 and in parallelism ftherewithupnl-apair; ofnlaterally i fpo'sitioned Iparallel rods I2 `and I3; the iylongitudinal spacing of which is; maintained bymean's of a pair of llink members: III1 and I5, which make loose` fits; against theiopposite; edges of the "base i I0 and'beammember `l I. The said rod supports I2 and I'3'defne1anfend supported-span portion Z'Iiand-a` cantilever portion 26. The links- Mand I5 areffretained 1in; fposition by means of. heads formed upon the exposed lends; of `the Isaid rods I2 landl lf3 I as-bestl: shown-iat I 6:in Figures 41: and n 2,` or yby other suitable means `:such` "as by soldering.` The JbeamyIzI andbasememberyl areheldyin substantial?parallel' assembled'.relationshipmfith i span portion. The 'forcefwto` be, measuredl is i adapted tqbeappiied ai; the apprpximatmcente of the "short, end supportedspan portion of the beam vto produce a 'deflection which is a: func-.

tionof the;` magnitude of theapplied force. ,n |Il'his deflection iis reiected intothe overhanging cantif lever lspan as` an @angular` movement about itsr inner support andthe resultantlmovementiofthe freeend `o1 the relatively long cantilever span then constitutes a magnified measure oftthe said.

deflectionand hence in turna measure ofthe ap-` pliedrorce to be gauged. w n Other objects and features of novelty of the invention `will be evident hereinafter.

In the drawing wherein a preferred embodi-` ment of the invention is shown by way Yoi il1us. tration and in which the same reference numerals refer to the sameor similar elements:

` Figurel is an isometric View `of the genera assembly of the apparatus. H

n yFigure 2 is a side elevationof thedevicel show-` ingwthe` electrode tips in `fragmentary'viewwin normalposition for the application of `the-force tobe measuredg n one another', =up0n fthe-befo'rementioned l spacing rodstl2r-andi I`3 bymeans ofi; rivets I8-2 I which pass through coaxially l[aligned: holes iniboth the beam II andabase' andzthrough arpairzof opposit-ely `positioned ,clamping plates 23 and '24.; The heads yofhthel jrivets.A 18g-2 I are r preferably` countersunk intofthesaidclainpingl plates 23` `and Mandare not driveni tight :but arevleftwithsuili'-K cient slacky Lto sallowV deflection ofthe 'beam'fand baseunder 'the applied force :Without zbinding,4 as hereinafter-described. y Adjacent the "free end" 25 fof ythe cantilever portion 2liA of the" beamwl Iran angularrshapedsupporting pedestal 129 is attached :to the base :CIU by means of-" a: pair of r suitable f rivets Vor machine screws as shown :atw An uoverhanging; bifurs catedprojection- 32 of thepedestal-29isprovidd y with a drilledopening 33 adapted` to receive. and n clamp the cylindrical'shank35fof a dial indicator type of micrometergauge;asshownfatSpin such a -positiontover the; free 'end of :the beam III` that the actuating plunger 37I-`ofthe said indicator may` bear upon the upper surface of the 'beam adjacent the `outer funsupported lend thereofg as shown atSB. .w v i `Atarget indicating-thel proper' position f apk plication of the electrode tiprt'dthe'inlstrunient when pressure is lt bei measured, as" illustrated at 319 and1 Main; Figure 2, isf indicated 'byl the CIS'S- by bending the bar stock back upon itself to form a U shaped unit as shown at 45 in Figure 4. 'In this arrangement, the rod I3 ,whichconstitutes a common support for the inner en'd of the' end supported span 21 and the cantilever 26, may be retained in proper position by any'suitable device such as for example by spot welding .tov

the inner surface of either the base member I0 or the beam` II, but to avoidrestraint'atfthis point, it preferably should not beiiv'eldedtol both. Thecoverl plates 23 and 24 in this case may be fastened to theouter surface ofthe'U shaped unit at the point where .electrode pressure is applied, by means *of aplastic adhesive or by means of suitableclips, 'not' shown.

The 'operation is as follows:

Thegauging 'deviceis inserted 'between the welding'tips 39 and 4`Il'which are closed asv shown in 'Figure' 2to bring the Velectrode ends'fto bear upon the opposite plates 23 land 24 at 'a point approximately centrally located with respect. to' the supporting rods .I and I3 `as indicated by the beforementioned position guide lines 4I' and 42 andv circle v43 yscribed onto theup'per plate 24.

As pressureY corresponding to the welding pressure' cycle is appliedlto .the electrodes 39 and 49 the'ends of which bear upon theopp'osite plates 23 and' 24,- the resultant force is transmitted through to the center portion of Vthe beam span 21 carried between the supports I2 and I3 causing a'bending'stre'ss which results in 'an inward deflection. This deflection causesa counterclockwise angular rotation ofthe beam in the region of the support I3 as viewed in Figure 3, which in turn'is reflected in an'amplifled upward motion of the free outer end 25 of the canti-` leverportion 2,6 of beam Il. Y The plunger 31 bearing at 38 upon the outer end of the beam I I isrthereby displaced vvertically a distance which isan amplied function of the degree of bending .of the beamv inthe span 21 between `the rod .supports'IZ and I3 under the electrode forces,'the degree of said-amplification being determined by the rati'o' ofthe distance between supports I2 and I3 and' thelength of the cantilever 26. The movement of the dial indicator pointer'48 over 'this'. scale 49 is a further magnified measure of the displacement of thev plunger 31 and hence a greatly magnified measure of the applied electrode forces.

vBy placing this 'device between tips similar to those shown at 39 and 40 but which lare incorporated in a testingmachine by means of which known' compressive forces may be applied to the instrument, the graduations of the indicator'dial 49 may readily be calibrated to read directly in anyunits of electrode force desired or a calibration curve may be established 'by means of which the readings of the standard graduations of the dial 49 maybe readily transposed into corrected pressure or force values.

That portion of the base I0 lying between the supports. I2 vand I3 and to which thelower electrode tip pressure is applied also flexes under the bending stress thus applied in a manner similar to that of the beam II which adds to the relative angular movement of the base I0 and Vthe cantilever portion 26 of the beam II about inch thick. The clamping plates 23 and 24 may be constructed of a suitable metal, but preferably of fibre, plastic, or the like insulating material,'such as for example, Micarta. The rods I2 and. I3 may be steel drill rod stock approximately le inch in diameter and the retainer links I4 and I5 of Phosphor bronze. The materals and dimensions may be Widely varied to suit the conditions to be encountered and range of forces `to be gauged.

The foregoing is merely illustrative of a method and apparatus of the invention and is not to be limiting.y The invention includes any method and apparatus which accomplishes the same resultswithin thescope of the claimsf l. A force gauge characterized by being of relatively thin construction adapted tomeasure the force between spotY Weld .electrodes in substantially their normal operating positions with respect to one another, comprising in combination a base member, a beam supported closely adjacent to and in substantial'parallelism with said base` member upon two supports,said supports being spaced apart longitudinally a distance relatively. short with respect to the length of said beam and thereby defining a relatively short end-supported span portion and an integral, relatively long cantileverY portion of said beam, said end-supported span portion being adapted to receive a transverse concentrated loading corresponding to the force to be measured and means attached to the end portion of said base member and'adapted vto be actuated by lateral displacement of the end of said cantilever portion .with respect to said base'member to indicate relatively the magnitude of said force.`

2..A' force gauge characterized byY being of relatively thin construction adapted toV measure the force betweenv spot ,weld electrodes in substantially their normal voperating positions with respect `to one-another,v comprising in combination a ibase member, abeam supported .closely adjacent to and' in substantial parallelism with said base member upon twosupports, said supports being spaced apart longitudinally a distance relativelyshortWithrespect to the length ofsaid beam and said base members,`and thereby defining relatively short end-supported span portions and adjacent relatively long projecting cantilever portions of said b eam and said base members, said end-supported span portions being adapted to receive a transverse concentrated loading corresponding to the force to be measured and means attachedto the end portion of one of said projecting cantilever portions and coupled with the' endportion of the other adjacent cantilever portion adapted to be actuated by lateral displacement/'of the ends of said cantilever 'portions with respect to one another to indicate relatively the magnitude of 'said force.

3. A force gauge in accordancewith claim 2 in which the said beam and base members are` integrally joined at one of said supports to form f the force between spot weld electrodes in sub-" stantially their normal operating positions with respect to one another, comprising in combination a base member, a beam supported closely adjacent to and in substantial parallelism with said base member upon two roller pivots, said rollers being spaced apart longitudinally a distance relatively short with respect to the length` of said beam and thereby defining relatively short simple span` portions and adjacent relatively long projecting cantilever portions of said beam and base members, link members extending along the sides of said simple span portions I of'said beam and base members to retain said 'roller pivots in longitudinal spaced relationship` between said beam and said base members, means to retain said link members and said roller pivots associated therewith in predetermined position with respect to said beam and said base member, said simple span portions intermediate said roller pivots being adapted to receive a transverse concentrated loading corresponding to the force to be measured, `and means attached to theend portion of one of said cantilever portions and coupled with the end portion of the other adjacent cantilever portion; and adapted to be actuated by lateral displacement ofthe ends of said cantilever portions with respect to one another, to indicate relatively the magnitude of said ap-` plied force.

5. A force gauge in accordance with claim 4 with a relatively thin layer of insulation xed to the external surface of at least one of said simple span" portions at a point adapted to receive the force of a spot'welder electrode.

6. A force gauge characterized by being of H `relatively thin construction adapted to measure the force between spot Weld electrodes in substantially their normal operating positions with respect to onel another, comprising in combination a base member, a beam supported closelyv adjacent to and in substantial parallelism with said base member upon two supports,said beam and base members being integrally joined at one oi said supports to form a unitary structure, and said supports being spaced apart longitudinally a distance relatively short with respect to the 4length of said beam and said base members', and

thereby-defining relatively `short end-supported span portions and adjacent relatively long projecting cantilever portions of said beam and said base members, said end-supported span portions being adapted to receive a transverse concentrated loading corresponding to the force to be measured and means attachedto the end portion of one of said projecting cantilever portions and coupled with the end portion of the other adjacent cantilever portion adapted to be actuto indicate relatively the magnitude of said force.

ROBERT C. BURT. 

